Blow torch fuel and method of burning same



May 15, 1962 N. L. EMMONS ET AL BLOW TORCH FUEL AND METHOD OF BURNING SAME Filed March '7, 1955 m .rzjoou 20 m mm R m a 5.520. m w m 2 2338 a m MW m m mmfi H Al Juan MP. m m MN I mm w Q Fzjoou m 2 8 \2 B w z mota Patented May-15, 1962 The present invention relates to 'a fuel for blow torches, and relates in particular to a suspension or dispersion of a metal powder in a liquid, and to a method of burning the same.

It has been proposed to employ metal powder as a fuel for a blow torch for cutting through metal, ceramic material, concrete and the like. In such apparatus the powdered metal mixed with oxygen orwith a fuel gas, is

longer storage periods, the presenceof inhibitor is desirable, and any suitable material Which inhibitslor retards the reaction of aluminum. with Water at ordinary temperatures'may be employed, the preferred inhibitor being potassium or sodium dichromate.

agent is preferred. The dispersing agent helps to prevent or retard settling of the metal powder in'the water, so as burned at the torch tip to provide a hot flame. 'The'operation of such torches requires that the metal powder be carried in the gas streameither the oxygen or fuel gasand this involves difliculties in securing uniform dispersion of the metal powder, andjinvolves complicated equipment to proportion the powderand gasand to prevent flash back.

In the oxygen-fuel gas type of torch, the amount of metal powder that can be introduced into the fuel gas line is quite limited, and the main benefit of introducing metal powder is to fluidize the slag in the cutting operation. In the oxygen-metal powder torch, fuel gas serves mainly as an igniter, the flame being self propagating after ignition, and very high temperatures can be attained. However, the proportioning of the metal powder and oxygen involves relatively complicated apparatus and complicated safety devices are necessary to prevent flash back and render the operation of such a torch safe.

It is an object of the present invention to provide a fuel comprising essentially a finely divided oxidizable metal dispersed in a liquid which will flow freely through small orifices without clogging.

Still another object is the provision of a blow torch fuel comprising a finely divided metal dispersed in a liquid carrier, which upon being burned will produce a flame having the ability to cut through rock, clay, concrete and other ceramic or earthy materials.

Another object is the provision of a metal powder fuel which can be burned in a blow torch of simple construction and in which complicated mixing, feeding or safety controls are not required.

Another object is the provision of a, liquid metal powder fuel composition which has a relatively high threshold kindling temperature, and Will keep. itself ignited in a bore hole.

According to the present invention we provide a fuel comprising a finely divided metal capable of sustained combustion, dispersed in a liquid carrier which may be combustible or not. The fuel mixture is preferably compounded with a surface active material or dispersing agent to assist in keeping the powder in suspension, and the suspension may contain substances which combat the thixotropic tendency of the suspension.

It is preferred to employ aluminum powder with water as the liquid. carrier for.seve'ral reasons. However, as water and aluminum powder react in storage such a mixto maintain the mixture in free flowing condition, and so the mixture can be stored without continuous agitation. The reactions which occur in the burning of the fuel are not known with certainty, but it is believed that the metal. reacts with the water toproduce hydrogen, and that the metal is converted topits oxide by direct union withoxygen and by reaction with the water. The heat produced by direct union of the metal with oxygen, the reaction of the metal with water, and burning'ofth'e resulting hydrogen is substantially'equivalent to theheat' produced by direct union of the metal with oxygen. Although mixtures with water containing as little as about 20% of metal powder may be burned, it is preferred to employ an excess of metal powder over the theoretical amount indicated in the following equation; metal+ water-metal oxide-l-hydrogen. For any particular metal ture should be used shortly after it is prepared. For

the theoretical proportion will vary, depending on the valence of the metal and its atomic weight. The excess of metal over the theoretical amount indicated above is limited by the fluidity of the mixture, and in general the ratio by weight may be as high as about 1.8 metal powder to water, the preferred ratio being about 1.5.

The metals capable of use in the present invention are those above the second series in the periodic system, the non-rare exothermic metals being preferred, and aluminum, iron, titanium and zirconium are mentioned by way of example. produce a more fluid slag, or to help sustain combustion, certain mixtures of these metals may be employed, or the fuel may contain in addition, othermetals below hydrogen in the electromotive series which react slowly or not at all with water at normal temperatures but which react vigorously with water at elevated temperatures, as for example, zinc, magnesium, or cadmium.

The mixture of water and metal powder is not combustible at ordinary temperatures, nor will the mixture detonate. Contrary. to expectations the presence of water does not prevent the blowtorch flame producing a temperature well above the melting point of concrete and For some purposes electrolytes or reactive metal salts are employed which decompose when heated to yield oxygen, "or otherwise react with the powdered'metal. Examples 'of suitable metal salts are the halides, chlorates, nitrates,

perchlorates of metals or of ammonium, for example, sodium chloride, chlorate or perchlorate, potassium ni- Also, where longer storage is desired the presence of a dispersing For certain purposes, as for example, to

trate or chlorate, calcium chlorate, nitrate or perchlorate, and ferric nitrate or ferrous perchlorate. Such salts, if soluble in water, serve as electrolytes to modify the thixotropic properties of the dispersions, but where an insoluble oxidizing salt is employed, it is desirable to employ a soluble electrolyte in addition thereto to control the thixotropic action. The amount of electrolyte or oxidizing salt employed is on the order of about five percent. An additional advantage residing in the presence of reactive metal salts, of the type above specified, is that after kindling of the flame occurs, the mixture will remain ignited when directed against a sufficiently heated surface, such as the wall of the bore hole, without the igniter gas. Sodium chloride and sodium nitrate are particularly suitable for this purpose.

Among the powdered metals usable in this invention, powdered aluminum is preferred. Aluminum powders are commercially available in the form of flakes and granules, the flakes generally having a thickness on the order of about five millionths of an inch with a length or width several hundred times the thickness, whereas the granules are more or less elongated to spherical and have a length or width on the order of two or three times the thickness. Aluminum powders are available in various mesh sizes, and in general We employ granular powders of two hundred mesh or finer, the four hundred mesh powders being preferred. As atomization of the liquid fuel and oxygen in the torch is highly desirable, the granular powders are preferred where the atomization involves the flow of the liquid fuel mixture through fine orifices, as the flake particles tend to temporarily clog the orifices, so as to cause nonuniform atomization of the mixture, and the finer powders are preferred as they offer a greater surface area per unit of weight, and therefore present a greater surface to the action of oxygen. However, with suitable equipment flake powders may be employed, although they are more costly than the granular powders.

In operation,'the flow of oxygen and fuel should be adusted to the proper proportion to secure efficient combustion. Proportioning may be accomplished by flow through fixed orifices, at pressures which are adjustable to secure the desired flow, or by adjusting the sizes of the orifices involved, or by adjustment of both factors. As the mixture of oxygen and fuel has a high threshold kindling temperature the atomization or mixing may be carried out in the torch before the burner tip is reached, the igniter or kindling flame being provided at the tip by acetylene, or any other suitable fluid fuel. When burning in open air it is preferred to continuously maintain the igniter flame, although in boring a hole, the igniter fuel may be shut off under certain conditions because the heated wall of the hole may provide suflicient heat to maintain ignition.

In the accompanying drawing there is shown a preferred construction of blow torch by Way of example, for burning the new fuel, and the invention will be described in connection therewith and the following illustrative examples. In the drawing,

FIGURE 1 is a cross sectional view of a blow torch with parts broken away, and

FIGURE 2 diagrammatically illustrates the operation of the torch.

Referring to the drawing, the torch comprises a head 1 with threaded sockets 2, 3 to which are connected respectively an oxygen line 4, and a fuel line 5. The head has a chamber 6 which receives a mixing nozzle 7, the nozzle having a passageway 8 therethrough connecting with an enlarged passageway 9. The nozzle and head are coupled in any suitable manner. An inclined passageway -11 connects chamber 6 with passageway 9. As chamber 6 receives the liquid fuel it will be seen that the liquid fuel is introduced into the oxygen stream flowing through passageway 9. If desired, a similar arrangement may be provided in advance of passageway 11 to introduce air, as under certain conditions a mixture of about one third oxygen and two thirds air may be employed.

The nozzle 7 connects with a torch barrel 12 terminating in a removable tip 13, and a jacket 14, surrounds the barrel. Cooling water is introduced into the barrel by an inlet tube 15, and the water discharges at the outlet tube 16. An igniter gas tube 17 extends through the jacket and has branch connections to a ring of orifices 18 in the end of the jacket. The burning igniter gas issuing from these orifices ignites the mixture of oxygen and fuel issuing from the tip 13.

The arrangement for supplying fuel to the torch is shown in FIGURE 2. The tank 19 contains the mixture of powdered metal and liquid, which is Supplied by pipe 21 to a pump 22 The pump supplie the mixture to the torch by pipe 5, and a return line 23 is connected back to the tank 19 in advance of valve 24. Valve 24 is adjusted to supply the desired flow of fuel to the torch, and excess fuel delivered by the pump is returned to the tank by line 23 and helps to maintain the mixture in the tank agitated. The size of pipes 5 and 23 are such as needed to maintain the desired pressure in line 5. A shut ofl? valve 25 may be provided in line 5. l p

The compositions are illustrated by the following examples:

1 Marasperse is the trade name ota wetting or dispersing agent.

The aluminum powder used is a 400 mesh granular powder, and the iron powder is cast iron powder of 400 mesh. The ingredients are mixed in any desired order until a thorough suspension is obtained.

In using the torch the following sequence of operation is employed: the igniter gas is turned on and ignited, the fuel is turned on, and then the oxygen i turned on. On shutting down the torch the fuel is first stopped, then the oxygen, and then the igniter gas. y Y

The ability of the flame to cut through material depends on the ratio of oxygen to fuel. In operation, the fuel is supplied at a constant rate and the oxygen pressure is varied to produce the best flame. The cutting rate is slow at first but after the hole has reached a depth of about one half inch the cutting action increases. The fuel mixtures containing sodium chloride or sodium nitrate (Examples 3 and 4) continue to burn in the hole after the igniter gas is turned off so that, after about one minute of operation the ingiter gas may be turned off, if desired. The boring rate in concrete block is about one inch per minute.

We claim as our invention: 7

1. A normally liquid fuel composition for a blow torch consisting of essentially: a mixture of water and a powdered exothermic oxidizable metal above both the first series in and the first group of the periodic system and having a valence ranging from 210 4, said metal powder being present in the ratio range of about 1:4 to 1.8: 1 parts by weight metal to Water.

2. The fuel composition of claim 1 whereini the metal is granular aluminum powder. V

3. The fuel composition of claim 1 including: a dis persing agent of a type that aids in preventing the metal powder from settling in the water.

4. The fuel composition of claim 1. inclu ing: an oxidizing salt. a

5. The fuel composition of claim 1 wherein: the metal is a mixture of granular aluminum powder and iron powder.

6. A method of producing high temperatures comprising: providing the fuel composition of claim 1; placing a supply of said composition under pressure; continuously releasing a stream thereof into a mixing chamber; feediug a stream of oxygen into said chamber at a rate providing a combustible mixture with said composition; and propelling said mixture into a region heated to the kindling temperature of said mixture.

References Cited in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS Australia June 14, 1934 

1. A NORMALLY LIQUID FUEL COMPOSITION FOR A BLOW TORCH CONSISTING OF ESSENTIALLY: A MIXTURE OF WATER AND A POWDERED EXOTHERMIC OXIDIZABLE METAL ABOVE BOTH THE FIRST SERIES IN AND THE FIRST GROUP OF THE PERIODIC SYSTEM AND HAVING A VALENCE RANGING FROM 2 TO 4, SAID METAL POWDER BEING PRESENT IN THE RATIO RANGE OF ABOUT 1:4 TO 1.8:1 PARTS BY WEIGHT METAL OF WATER. 